Effect of X-Ray Dose on the Protective Action and Persistence of Rat Bone Marrow in Irradiated, Penicillin-Treated Mice

¹ From the Division of Biological and Medical Sciences, U. S. Naval Radiological Defense Laboratory, San Francisco, California

Rat bone marrow cell suspensions injected together with penicillin into mice a few hours following exposure to low lethal (ld₂₀) dose of x-rays (600–680 r) elicited no deleterious effect on percentage of survivors at 30 days, or on mean survival times, when compared to irradiated controls treated with penicillin only. Following ld₇₀–ld₁₀₀ x-rays (720–770 r), the injection of rat bone marrow plus penicillin resulted in marked increases in percent survival at 30 days, as well as later survival. Thus, at 770 r (ld₁₀₀), 40% of the treated mice were still alive at 150 days. The single injection of penicillin (3840 u/mouse) together with rat marrow following 870 r exposure, significantly decreased the 30-day mortality, as compared to irradiated mice receiving rat bone marrow alone. In general, rat granulocytes in the peripheral blood, as determined by the alkaline phosphatase histochemical technique, persisted longer at the higher doses of x-radiation. The data indicate that LAf₁ mice exposed to x-rays in the midlethal dose range are able to ‘recognize’ and dispose of injected foreign rat cells within a few weeks without suffering an enhanced mortality.

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